Audio Video Forensics

Unlike other forms of forensic evidence, audio and video recordings can provide a real-time, eyewitness account of a crime so investigators can watch or hear what transpired. For instance, a surveillance video captures a bank robbery in progress, or a hidden camera records an undercover sting operation. Over the past decade, sources of recorded audio and video that can assist in an investigation have increased exponentially. Closed circuit television systems (CCTV) and video and audio recorders can be found in businesses, at traffic intersections, parking lots, bank machines, on police-vehicle dashboards and of course, in cell phones.

Principles of Forensic Audio and Video Analysis:-

To assist in an investigation, forensic experts can repair, recover, enhance and analyze audio and video recordings using an array of scientific tools and techniques.

Repair and Recovery of Evidence:-

Before audio and video evidence can be analyzed, it may first need to be repaired or recovered from damaged media or a damaged recording device. Repairing evidence is especially common for analog and digital magnetic tape. It may need to be spliced back together or put into a new audio/video housing in order to recover the audio or video. In today’s digital world, CDs, DVDs, cell phones, portable cameras and other sources of digital media and recording devices can be damaged by heat, misuse, the environmental conditions of a crime scene, or simply on purpose by an offender. Even in these situations, the digital files can be recovered and used for analysis.

Evidence Enhancement:-

The most common function of forensic video and audio experts is to clarify a recording so that it is more apparent to investigators, attorneys and jurors what the evidence demonstrates. To enhance a video recording, filters can be used to adjust the brightness and contrast, correct the color, crop and resize an image, enhance edge detail and reduce visual distortion. The speed of playback can also be adjusted to more accurately display the frame rate at which it was recorded. To enhance an audio recording, filters can be employed to improve clarity. This may entail removal of unwanted noise or enhancing the intelligibility of speech. Recordings will often be made in less than ideal circumstances, such as when someone is wearing a body wire. Utilizing audio engineering techniques may allow faint voices or events to be heard more clearly on playback.